Overview

Distribution

This species of crocodile is found in the Northern Territory of Australia and Queensland, and also in northern and western Australia.

Biogeographic Regions: australian (Native )

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Continent: Australia
Distribution: Northern Australia (Northern Territory, Queensland and Western Australia)  
Type locality: "Cashmere, upper Herbert River, Qld" (= Queensland), Australia.
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Physical Description

Morphology

Crocodylus johnsoni can reach a maximum length of three meters. It has a light brown body with darker bands on its body and tail and lighter brown bands on its snout. It has a morphologically distinct narrow snout with approximately 68-72 teeth total consisting of 5 premaxillary teeth, 14-16 maxillary, and 15 mandibular teeth. The body is covered with scales that are generally large and provide wide armor on the back.

Other Physical Features: ectothermic ; bilateral symmetry

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Ecology

Habitat

This species occupies various fresh water areas such as lagoons, rivers, billabongs, and swamps.

Aquatic Biomes: lakes and ponds; rivers and streams

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Habitat and Ecology

Systems
  • Terrestrial
  • Freshwater
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Trophic Strategy

This creature eats fish, insects, small invertebrates, amphibians, mammals, birds, and other small vertebrates. Large individuals may consume terrestrial prey.

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Life History and Behavior

Life Expectancy

Average lifespan

Status: captivity:
20 years.

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Lifespan, longevity, and ageing

Maximum longevity: 20 years (captivity) Observations: In conditions of scarce food, growth and sexual maturity are delayed in these animals (Lance 2003).
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Reproduction

The females nest in holes that are exposed on sandbars during the dry season from August through September. Mating occurs three to six weeks before laying. Clutches average in size between 13-20 eggs and hatch in about 65-95 days. Egg laying usually occurs at night. Eggs are faced with predation by monitor lizards and feral pigs. High and low temperatures (33-34C) produce female embryos while intermediate temperatures (32C) produces male embryos. The nests of eggs are left unguarded, but the mothers reappear in late October. At the end of the incubation period, the mothers carry the newly hatched young to the water in their mouths. The mothers then stay close to the young and protect them for a short period of time. In addition to being hole nesters, they are also sometimes called "pulse nesters" because all females in a given population nest within a brief three week period each season. Individuals reach reproductive maturity when they reach 1.5 meters in length.

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Crocodylus johnsoni

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
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Statistics of barcoding coverage: Crocodylus johnsoni

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

Long-term aboriginal hunting did not significantly affect the population despite advances made in tanning processes at the end of the 1950s that allowed the skins of this species, instead of those of the preferred saltwater crocodile, to be used as leather. Hunting did cause a decrease in populaton size but protective measures were taken in the early 1960s. In western Australia they were protected by law in 1962, and in 1964 in the Northern Territory. Queensland did not pass its protective laws until 1974. Illegal hunting continues but the main threat is the destruction of habitat. Small scale ranching and farming of these crocodiles exists.

IUCN Red List of Threatened Species: lower risk - least concern

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IUCN Red List Assessment


Red List Category
LR/lc
Lower Risk/least concern

Red List Criteria

Version
2.3

Year Assessed
1996
  • Needs updating

Assessor/s
Crocodile Specialist Group

Reviewer/s

Contributor/s

History
  • 1988
    Vulnerable
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Vulnerable
    (IUCN Conservation Monitoring Centre 1986)
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Management

Conservation Actions

Conservation Actions
It is listed on CITES Appendix II.
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Relevance to Humans and Ecosystems

Benefits

Occasional attacks on humans have been reported.

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Humans benefit from this species by using it for its meat, eggs, and its leather-producing hide.

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Wikipedia

Freshwater crocodile

"Freshie" redirects here. For the drink mix, see Freshie (drink mix).

The freshwater crocodile (Crocodylus johnsoni or Crocodylus johnstoni; see below), also known as the Australian freshwater crocodile, Johnston's crocodile or colloquially as freshie, is a species of reptile endemic to the northern regions of Australia.

Unlike their much larger Australian relative the saltwater crocodile, freshwater crocodiles are not known as man-eaters and rarely cause fatalities, although they will bite in self-defense if cornered.

Taxonomy and etymology[edit]

When Gerard Krefft named the species in 1873, he intended to commemorate the man, Sir Henry "Harry" Hamilton Johnston, who first reported it to him. However, Krefft made an error in writing the name, and for many years the species has been known as johnsoni. Recent studies of Krefft's papers have determined the correct spelling of the name, and much of the literature has been updated to the correct usage. However, both versions are still extant. According to the rules of the International Code of Zoological Nomenclature, the epithet johnsoni (rather than the intended johnstoni) is correct.[4]

Characteristics[edit]

The freshwater crocodile is a relatively small crocodilian. Males can grow to 2.3–3 m (7.5–9.8 ft) long, while females reach a maximum size of 2.1 m (6.9 ft).[4] Males commonly weigh around 70 kg (150 lb), with large specimens up to 100 kg (220 lb) or more, against the female weight of 40 kg (88 lb).[5] In areas such as Lake Argyle and Katherine Gorge there exist a handful of confirmed 4 metres (13 ft) individuals. This species is shy and has a more slender snout and have a slightly smaller teeth than the dangerous saltwater crocodile. The body colour is light brown with darker bands on the body and tail—these tend to be broken up near the neck. Some individuals possess distinct bands or speckling on the snout. Body scales are relatively large, with wide, close-knit armoured plates on the back. Rounded, pebbly scales cover the flanks and outsides of the legs.[4]

Distribution and habitat[edit]

Freshwater crocodiles are found in the states of Western Australia, Queensland, and the Northern Territory. Main habitats include freshwater wetlands, billabongs, rivers and creeks. This species can live in areas where saltwater crocodiles cannot, and are known to inhabit areas above the escarpment in Kakadu National Park and in very arid and rocky conditions (such as Katherine Gorge, where they are common and are relatively safe from saltwater crocodiles during the dry season). However, they are still consistently found in low-level billabongs, living alongside the saltwater crocodiles near the tidal reaches of rivers.

In May 2013, a freshwater crocodile was seen in a river near the desert town of Birdsville, hundreds of kilometres south of their normal range. A local ranger suggested that years of flooding may have washed the animal south, or it may have been dumped as a juvenile.[6]

Biology and behavior[edit]

They compete poorly with saltwater crocodiles; however, this species is saltwater tolerant. Adult crocodiles eat fish, birds, bats, reptiles and amphibians, although larger individuals may take prey as large as a wallaby.

One has even been filmed being eaten by an Olive python after a struggle that lasted for an estimated 5 hours.[7]

Reproduction[edit]

Eggs are laid in holes during the Australian dry season (usually in the month of August) and hatch at the beginning of the wet season (November/December). The crocodiles do not defend their nests during incubation. From one to five days prior to hatching, the young begin to call from within the eggs. This induces and synchronizes hatching in siblings and stimulates adults to open the nest. It is not known if the adult that opens a given nest is the female who laid the eggs. As young emerge from the nest, the adult picks them up one by one in the tip of its mouth and transports them to the water. Adults may also assist young in breaking through the egg shell by chewing or manipulating the eggs in their mouths.[8]

Conservation status[edit]

Freshwater crocodile at Australia Zoo

Until recently, the Freshwater crocodile was common in northern Australia, especially where saltwater crocodiles are absent (such as more arid inland areas and higher elevations). In recent years, the population has dropped dramatically due to the ingestion of the invasive Cane Toad. The toad is poisonous to freshwater crocodiles, although not to saltwater crocodiles, and the toad is rampant throughout the Australian wilderness.[9] The crocodiles are also infected by Griphobilharzia amoena, a parasitic trematode, in regions such as Darwin.[10]

Danger towards humans[edit]

Although the freshwater crocodile does not attack humans as potential prey, it can deliver a nasty bite. There have been very few incidents where people have been bitten whilst swimming with freshwater crocodiles, and others incurred during scientific study. An attack by a freshwater crocodile on a human was recorded at Barramundi Gorge (also known as Maguk) in Kakadu National Park and resulted in minor injuries; the victim managed to swim and walk away from the attack. He had apparently passed directly over the crocodile in the water. However, in general, it is still considered safe to swim with this species, so long as they are not aggravated.[11]

Gallery[edit]

References[edit]

  1. ^ Crocodile Specialist Group (1996). Crocodylus johnsoni. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 31 January 2010.
  2. ^ "Crocodylus johnsoni". Integrated Taxonomic Information System. 
  3. ^ [ . . johnstoni means "of Johnston", derived from the name of the first European to discover and report it to Krefft. Unfortunately Krefft misspelled the name "johnsoni" in his initial description and his subsequent correction was ignored until 1983 when the nomenclature was reviewed thoroughly by Hal Cogger (Cogger 1983). Although the majority of scientific literature, including all Australian Federal, State and Territory legislation has been using "johnstoni" correctly since then, the uncorrected version is still popular especially in the US on the basis of a later taxonomic review (King and Burke 1989) that ignored Cogger's revision. http://crocodilian.com/cnhc/csp_cjoh.htm Crocodilian Species List, Crocodylus johnstoni (KREFFT, 1873) ]
  4. ^ a b c Adam Britton. "Crocodylus johnstoni". Florida Museum of Natural History. Retrieved 16 June 2009. 
  5. ^ [1]
  6. ^ "Crocodile turns up in river near Birdsville". 23 May 2013. Retrieved 2013-05-25. 
  7. ^ http://www.telegraph.co.uk/travel/destinations/australiaandpacific/australia/10672439/Snake-eats-crocodile-in-battle-at-Australian-lake.html
  8. ^ Somaweera, Ruchira; Shine, Richard (September 2012). "Australian freshwater crocodiles (Crocodylus johnstoni) transport their hatchlings to the water". Journal of Herpetology 46 (3): 407–411. doi:10.1670/11-056. 
  9. ^ "Crocodiles falling victim to cane toads". ABC News. 29 December 2008. 
  10. ^ T. R. Platt, D. Blair, et al. (1991). "Griphobilharzia amoena n. gen., n. sp. (Digenea: Schistosomatidae), a parasite of the freshwater crocodile Crocodylus johnstoni (Reptilia: Crocodylia) from Australia, with the erection of a new subfamily, Griphobilharziinae". Journal of Parasitology 77 (1): 65–68. doi:10.2307/3282558. JSTOR 3282558. 
  11. ^ http://aebrain.blogspot.com/2003/09/how-embarressing.html
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